Endemic sites of Blastomyces dermatitidis are being determined using the skin test in dogs and following up recent cases. Studies will be conducted at these sites to determine the foci where the fungus occurs in nature. Soil and other specimens will be tested for the fungus and small animals are being trapped and examined for blastomycosis. Methods of isolating the fungus from contaminated specimens will be evaluated and tested in the field. The characteristics of high endemic sites will be compared to low ones for factors common or unusual in each area.